Foamed resin structures are useful in a wide variety of applications. The foamed resin is lightweight and provides good insulating properties. In some applications, it is desirable to provide the foamed resin structure with a solid resin outer layer to increase the strength of the structure. Various methods have been employed to manufacture such structures. In a typical method, a foamed resin core is first preformed and cured in a foam die. Then the foamed resin core is transported to a coating chamber where a liquid resin coating is applied and cured into a solid resin. This method is relatively time-consuming, and as a result, it may not be as economical as a simpler method. Another disadvantage is that the solid resin coating may not strongly bond to the foamed resin core.
Other methods are known for producing structures with foamed resin cores and solid resin outer layers; e.g., U.S. Pat. Nos. 3,533,901 to Sutker, 3,895,087 to Ottinger et al., 4,645,710 to Baitinger et al., 5,142,835 to Mrocca, and 5,286,320 to McGrath et al. disclose various methods for producing such structures. However, most of the known methods suffer from various drawbacks. For example, some methods require the separate formation of the core and outer layers of the structure, as in the Baitinger et al. and Mrocca patents, where a resin facing sheet or a resin-impregnated fibrous mat is adhered to the outer surface of a foamed resin core. The Ottinger et al. patent describes a molding technique where a foamed resin core is molded onto a preformed resin film.
Thus, it would be desirable to provide a method for producing a foam-containing structure which is simple and economical, and which produces a structure having a strong bond between a solid resin outer layer and a foamed resin core.